# Copyright 2024 Superlinked, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import threading
from functools import wraps

from beartype.typing import Any, Callable, Type, TypeVar

T = TypeVar("T")


def singleton(cls: Type[T]) -> Callable[..., T]:
    instances: dict[Type[T], T] = {}
    lock = threading.Lock()

    @wraps(cls)
    def wrapper(*args: Any, **kwargs: Any) -> T:
        if cls not in instances:
            with lock:
                if cls not in instances:
                    instances[cls] = cls(*args, **kwargs)
        return instances[cls]

    return wrapper
